This application is based on applications Nos. H11-149893, H11-236724, and H11-372604 filed in Japan, the contents of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a semiconductor memory card that stores audio data, still image data and control data, and to a playback apparatus, recording apparatus, playback method, recording method, and computer-readable recording medium relating to such a semiconductor memory card. In particular, the present invention relates to improved storage of audio data, image data and control data distributed as contents by a content distribution service, such as an electronic music distribution service.
2. Description of Background Art
Electronic music distribution enables users to purchase and receive music contents (e.g., songs and albums) via the Internet. Such technology has the potential to greatly change the market for recorded music and is gradually becoming possible as the necessary infrastructure is introduced. One way to store music contents that are obtained from an electronic music distribution service is on semiconductor memory cards whose portability makes them ideal. Accordingly, a great increase is expected in the demand for such cards.
Music contents are not restricted to merely containing audio data. As one example, xe2x80x9cmixed-mediaxe2x80x9d audio contents can include related images that are to be displayed when music is played back. Such mixed-media audio contents can be used for xe2x80x9ckaraoke softwarexe2x80x9d that is composed of a backing audio track and images for the lyrics of a song and a background. It is believed such mixed-media audio contents will also be subject to electronic music distribution, so that it is necessary to consider how such contents should be stored in a semiconductor memory card.
The following describes how mixed-media music contents are stored on a recording medium, such as a CD (Compact Disc), which is to say, how audio data and image data are conventionally stored on a recording medium.
To enable a player to play back music and display images, a conventional mixed-media music content is recorded onto a recording medium as multiplexed data produced by multiplexing audio data for the music with image data for the lyrics and/or background images. When the multiplexed data is reproduced, the image data can be displayed while the audio data is being played back.
A CD-Graphics disc is one example of a medium that enables image data to be displayed while audio data is being played backed by having such data multiplexed together. When producing a CD-Graphics disc, data is multiplexed in units composed of 16-bit main codes and subcodes. Audio data is assigned to the 16-bit main codes, while image data for lyrics, background images and the like is assigned to the subcodes. When playback commences for any of the music contents recorded on a CD-Graphics disc, the audio data assigned to the 16-bit main codes is successively played back while the image data assigned to the subcodes is successively displayed.
When audio data and image data are multiplexed together in this way, it becomes necessary to provide separate images to each music content in a music album. This means that in this conventional multiplexing method, a disc producer has had to go to the trouble of producing at least one image for each music content.
It is believed that fans of major recording artists will appreciate having a different image for each song (music content) on an album. Since such artists can expect to sell many copies of their albums, the cost of providing such extra material should be covered by sales.
However, minor artists cannot expect high sales for their work even if different images are provided for each song, so that the cost of providing such material may not be offset by sales.
In this way, the commercial effect that results from the money and effort expended in the production of images will greatly differ depending on whether the artist is popular. With conventional discs, however, it is necessary to assign at least one image to each music content regardless of how popular the recording artist is or of how many sales can be expected. As a result, producers are dissatisfied with conventional media.
It is an object of the present invention to provide a semiconductor memory card that can reduce the effort required when providing images for a plurality of audio contents that compose an album.
When images are displayed during the playback of audio contents, images that represent the lyrics of a song should only be displayed during the playback of the corresponding song. Background images, however, may be commonly used during the playback of any number of songs. As one example, when the songwriter or artist is the same, the same picture of the songwriter or artist can be used as a background image for a number of songs. It is believed that this will make it easy for disc producers to store music data (audio objects) and image data (picture objects) together.
The sharing of image data (still image objects) between a plurality of audio objects can be preferably achieved by a semiconductor memory card storing: an audio sequence including a plurality of audio objects; a plurality of still image objects; at least one piece of playback route information showing an order in which audio objects, out of the plurality of audio objects in the audio sequence, are to be played back; at least one piece of first pointer information, each of which corresponds to a piece of playback route information and specifies at least one still image object that should be displayed when the audio objects in the order indicated by the corresponding piece of playback route information are played back; and at least one piece of second pointer information, each of which corresponds to an audio object in the audio sequence and specifies at least one still image object that should be displayed only during playback of the corresponding audio object.
A plurality of audio objects in an audio sequence are played back in accordance with a playback order given in apiece of playback route information. Still image objects that are to be displayed as background images during the playback of the audio objects are indicated by the first pointer information corresponding to the playback route information. As a result, shared still image objects can be displayed during the playback period of the plurality of audio objects included in the audio sequence.
Since the same images can be used for a plurality of tracks, the same image or images can be displayed during the playback of a plurality of audio objects in an audio sequence that corresponds to an album by a minor recording artist. This reduces the cost and effort of producing images for such an album.
Conversely, a plurality of different images can be provided for display during the playback of each audio object in an audio sequence that corresponds to an album by a major recording artist. Displaying a number of different images for each track makes the album more appealing to customers, and so can improve sales.
When there are still image objects, such as for song lyrics, that are to be displayed separately to the background images only during the playback of a particular track, such still image objects can be specified using second pointer information to assign the still image objects to only the particular track.
Here, the semiconductor memory card may further store a plurality of symbolic counters, each of which corresponds to a still image object and shows whether the still image object is specified by any of the at least one piece of first pointer information and the at least one piece of second pointer information and, if so, how many pieces of first pointer information and second pointer information specify the still image object.
When deleting audio objects and audio sequences, the recording apparatus for a semiconductor memory card specifies the second pointer information for the deleted audio objects and audio sequences and the first pointer information for any deleted audio sequence. The recording apparatus then decrements the numbers assigned to still image objects to show how many pieces of first pointer information and second pointer information specify each object. When the number assigned to any still image object reaches zero, the recording apparatus assumes that no piece of first pointer information or second pointer information specifies the still image object and so deletes the still image object. By deleting unused still image objects in this way, the storage capacity of a semiconductor memory card can be used more efficiently.